The present invention relates to the delivery of agents such as therapeutic agents to tissue and, particularly, to the delivery of cells to tissue.
The following information is provided to assist the reader to understand the invention disclosed below and the environment in which it will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document. References set forth herein may facilitate understanding of the present invention or the background of the present invention. The disclosures of all references cited herein are incorporated by reference.
The treatment of disease by the injection of living cells into a body is expanding rapidly. There are many types of cells being used to treat an equally diverse set of diseases, and both types of cells and disease conditions are expanding rapidly. Xenogeneic cell therapies involve implantation of cells from one species into another. Allogeneic cell therapies involve implantation from one individual of a species into another individual of the same species. Autologous cell therapies involve implantation of cells from one individual into the same individual.
In an example of an allogeneic cell therapy, current phase II clinical trials of SPHERAMINE® by Titan Pharmaceutical of San Francisco, Calif. and Schering AG of Berlin, Germany, retinal pigment epithelial cells are harvested from eyes in eye banks, multiplied many fold in culture medium and placed on 100 micrometer diameter gelatin spheres. The spherical microscopic carriers or microcarriers greatly enhance the cells' survival when injected in the brain. The carriers are injected through needles into the putamen in the brain. The animal precursor work is described in several patents, including U.S. Pat. Nos. 6,060,048, 5,750,103, and 5,618,531, the disclosures of which are incorporated herein by reference. These patents describe many types of cells, carriers, and diseases that can be treated via the disclosed methods. In a rat, about 20 microliters (μl) of injected cells on carriers is sufficient to restore dopamine production to a damaged rat brain. The therapy was injected at the rate of 4 μl/min. This dosage scales to a total injected volume of 0.5 ml in the human brain, although it will have to be distributed over a larger region, probably via multiple individual injections on the order of the 20 μl mentioned above. Cell therapies for the brain and nervous system are discuss further below.
An example of an autologous cell therapy involves the harvesting of mesenchymal stem cell from a patient's bone marrow, concentration of the stem cells, and injection of the cells and other blood components into the heart muscle during open-heart surgery. Further examples include catheter delivered cell therapies, especially to the heart, laparoscopic delivered therapies, and transcutaneous therapies.
In external cell therapy for the heart, volumes of about 0.5 to 1.0 ml are injected into a beating heart. A multi-milliliter syringe is used to hold and deliver the injectate under manual activation. A challenge is presented in that when the heart is contracting, during systole, the tissue becomes relatively hard and tense. In diastole, the tissue relaxes. It is very difficult for a human to time and control a hand injection so that the proper volume is injected all in one period of diastole. In practice, an indeterminate amount of the injectate can squirt or leak out the needle track and is presumably wasted. In addition, it is desirable to uniformly and thoroughly treat the target areas of the heart, and to avoid puncturing the major blood vessels traversing the outside of the heart. These results can also be difficult to achieve with current manual injection practices. With the current state of practice, scar tissue is not injected or treated because it does not respond well, and the growth that does occur can sometimes create dangerous electrical conduction abnormalities.
Cell therapies are generally delivered by hand injection through a needle or catheter. The benefits of hand or manual injection are conceptual simplicity and familiarity for the doctor. However the simplicity is misleading. Many of the parameters of the injection are not and cannot be controlled or even repeated by that doctor, let alone by other doctors. Flow rate is, for example, very difficult to control manually, especially at low flow rates. The stick slip friction of normal syringes exacerbates this problem. Volume accuracy depends upon manual reading of gradations, which is physically difficult while squeezing the syringe and susceptible to human perceptual or mathematical errors. The use of common infusion pumps limits delivery to generally slow and very simple fluid deliveries. Infusion pumps have no ability to provide automatic response or action to the injection based upon any physiological or other measurement or feedback.
Tremendous variations in manually controlled injectate delivery can produce proportionally wide variations in patient outcomes. In clinical trials, this variation is undesirable because it increases the number of patients and thus cost and time needed to establish efficacy. In long term therapeutic use, such variation remains undesirable as some people can receive suboptimal treatment.
FIG. 1A illustrates the current manual state of the art. Cells are taken from a bag or other storage or intermediate container and loaded into a syringe. This procedure involves making and breaking fluid connections in the room air which can compromise sterility, or requires a special biological enclosure to provide class 100 air for handling. The syringe is then connected to a patient interface or applicator, which is commonly a needle, catheter, or tubing that is then connected to a needle or catheter. For many procedures, there is some type of imaging equipment involved in guiding the applicator or effector to the correct part of the body. For example, the imaging equipment can include X-ray fluoroscopy, CT, MR, ultrasound, or an endoscope. The physician views the image and places the applicator by hand. In some neurological procedures, a stereotaxic (or stereotactic) positioner or head frame is used to guide the applicator to the target tissue, deep in the brain, based on coordinates provided by the imaging system. The patient physiological condition is often monitored for safety, especially when the patient is under general anesthesia.
As discussed briefly above, medical research has demonstrated utility of implantation of cells into the brain and central nervous system as treatment for neurodegenerative disorders such as Parkinsons, Alzheimers, stroke, motor neuron dysfunction experienced, for example, by victims of spinal cord injury. As with other cell therapies, the mechanisms of repair are not well understood, but the injection of cells into damaged parenchymal tissue has been shown to recruit the body's natural repair processes and to regenerate new functional tissue as well as the cells themselves living and integrating into the tissue.
As with other cell delivery techniques described above, a long recognized, but unmet need in this field is a set of methods and devices that can provide precise, repeatable and reliable control of dosage of these therapeutic agents in actual clinical settings. Current manual approaches (as summarized above and in connection with FIG. 1A) do not address all of the needs required by new procedures. For example, there are no good methods for ensuring the parameters of cell viability, including spatial distribution, cell quantity, metabolic and electrical activity, in real time during the entire implantation procedure. These variables are affected by cell storage conditions, by the fluid dynamics of an injection (for example, flow, shear stresses or forces, fluid density, viscosity, osmolarity, gas concentration), by the biocompatibility of materials, and by the characteristics of surrounding tissues and fluids.
Deleterious effects of flow of cells through fluid paths are also not well addressed in current techniques. For example, Luer standard connectors are used almost universally in the current medical practice, including in fluid paths for cell delivery. An example of a lure standard connector 1 is show in FIG. 1B. FIG. 1B is taken from the standard ISO 594-1-1986, figure number 2. As the tapered sections of the male 1a and female 1b connectors mate, a dead space is created as indicated by 1c. In addition, the sharp transition in the fluid path at the end of the male luer, as indicated at 1d, can create turbulence and increase shear stress in the fluid and on the cells, resulting in cell damage or even death. Moreover, similar problems exist in commonly used fluid path elements other than connectors.
There are current methods for delivery of chemotherapeutic agents directly to the brain and other central nervous system structures (CNS) including, for example, convection enhanced delivery (CED) and other direct injection by needles, catheters, and syringes into CNS structures. These direct injections are an alternative to less effective intravenous drug delivery methods. Other approaches to drug delivery in the CNS include the placement of drug-impregnated hydrogel wafers (Gliadel®) directly into brain tissue for extended periods of time after tumor excision. In the case of Parkinson's disease treatment, dopamine-producing cells are assembled onto gelatin beads (SPHERAMINE®, Titan Pharmaceuticals), which are hand-injected through precision syringes into the brain. The effectiveness of these methods is typically monitored long after initial treatment with non-invasive imaging (CT, MR).
Examples of systems and methods for convection enhanced delivery to the brain and other solid tissue structures is described in U.S. Pat. No. 5,720,720, the disclosure of which is incorporated herein by reference. Although the '720 patent discloses methods of injecting liquid medications based on a biomechanical model of tissue, it does not address problems unique to the delivery of complex slurries of fragile neural cells. U.S. Pat. No. 6,599,274, the disclosure of which is incorporate herein by reference, discloses methods of cell delivery to the brain using catheter injection systems. Control systems are described in which the distribution and function of therapeutic cells, growth factors, or other proteins are monitored by various techniques of imaging, physical, chemical, and electrical measurement. The '274 patent mentions closed loop, real-time control of the cell infusion process based on imaging and measured properties. However, the '274 patent does not describe how the elements of a controlled cell storage system work together with an injection system to guarantee delivery of viable cells of correct dosage and associated growth factors into tissues of the CNS. U.S. Pat. No. 6,758,828 describes a cell storage system for maintaining the viability of cells injected into tissue, but does not describe an integrated control system for monitoring the viability of cells as they enter the patient and take up residence in the parenchyma, nor does it describe how cell viability can be monitored in vivo.
U.S. Pat. No. 6,749,833 discloses methods to sustain the viability of cells by limiting damage resulting from shear stresses during fluid flow. An apparatus is described which allows for continuous bolus flow or peristaltic flow by reducing these shear forces. It is not clear from the '833 patent how the viability of cells is to be measured after delivery of the cells into living tissue. U.S. Pat. Nos. 6,572,579, 6,549,803 and 6,464,662 attempt to address the problem of distributing a dose of biologically active material into tissue by means of direct catheter injection.
In addition to application of cell therapies to internal tissues such a heart tissue, brain tissue and central nervous system tissue, cell therapies have also recently been applied to skin. Dermatologists have been injecting drugs into the skin for years. Recently, injections of collagen, which can be thought of as a cell-less tissue, have become popular. Moreover, Intercytex of Cambridge UK has developed the ability to inject autologous dermal papilla cells for the growth of hair to treat baldness. The cells are harvested from a person, multiplied in culture, and then reimplanted into the same person. The implantation requires about 1000 injections of 1 microliter each.
Various aspect of delivery of agent to tissue and related aspects are also discussed in U.S. Pat. Nos. 5,720,720, 5,797,870, 5,827,216, 5,846,225, 5,997,509, 6,224,566, 6,231,568, 6,319,230, 6,322,536, 6,387,369, 6,416,510, 6,464,662, 6,549,803, 6,572,579, 6,599,274, 6,591,129, 6,595,979, 6,602,241, 6,605,061, 6,613,026, 6,749,833, 6,758,828, 6,796,957, 6,835,193, 6,855,132, Patent Applications Nos. 2002/0010428, 2002/0082546, 2002/0095124, 2003/0028172, 2003/0109849, 2003/0109899, 2003/0225370, 2004/0191225, 2004/0210188, 2004/0213756, and 2005/0124975, as well as in, PCT Published International Patent Application WO2000/067647, EP1444003, the disclosures of which are incorporated herein by reference.
Although various devices, systems and methods have been developed for delivery of agents, including therapeutic agent, to various types of tissue, it remains desirable to develop improved devices, systems and methods for delivering agents to tissue and, particularly, for delivering therapeutic cells to tissue.
The present invention, along with the attributes and attendant advantages thereof, will best be appreciated and understood in view of the following detailed description taken in conjunction with the accompanying drawings.